netdev - Re: [PATCH 03/14] net: tcp_memcontrol: properly detect ancestor socket pressure

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Date:	Sat, 14 Nov 2015 15:45:52 +0300
From:	Vladimir Davydov <vdavydov@...tuozzo.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...e.cz>,
	<netdev@...r.kernel.org>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel-team@...com>
Subject: Re: [PATCH 03/14] net: tcp_memcontrol: properly detect ancestor
 socket pressure

On Thu, Nov 12, 2015 at 06:41:22PM -0500, Johannes Weiner wrote:
> When charging socket memory, the code currently checks only the local
> page counter for excess to determine whether the memcg is under socket
> pressure. But even if the local counter is fine, one of the ancestors
> could have breached its limit, which should also force this child to
> enter socket pressure. This currently doesn't happen.
> 
> Fix this by using page_counter_try_charge() first. If that fails, it
> means that either the local counter or one of the ancestors are in
> excess of their limit, and the child should enter socket pressure.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Reviewed-by: Vladimir Davydov <vdavydov@...tuozzo.com>

For the record: it was broken by commit 3e32cb2e0a12 ("mm: memcontrol:
lockless page counters").
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